Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia
hmm, you should be able to.. I'll have to find the docs for phpBB and sus these permissions out better and fix that..
I thought I had them figured, but there are 3 sets of overlapping permissions (forum, group and user), and I havent grokked the interelationships between them yet. I'll look into it _________________ Great minds discuss ideas. Average minds discuss events. Small minds discuss people
Sun Jul 24, 2005 11:21 pm
Knightrous Site Admin
Joined: 15 Jun 2004
Posts: 8511
Location: NSW
Okay, this is a technical questions I've been wondering for a while. But today I found it relevent to actually ask the question. With all the talk of rewinding motors and making custom things, I was considering the possibility of making a different stator for a motor. The question is, can I make a stator out some 5mm laser cut steel or aluminium and still get the desired performance, or is it an industrail secret on how to make them involving quantum theory, magical metals and pages of M theory dumped in?
I noticed that all stators have funny score markings around the outside as shown below:
What is this and why is this done? I'm expecting this to become a mega tech fest between Jake and Brett, but anyone with some relevent information (Andrew, your good at this will all the unique experince you have) that they could share would be greatly appreciated!!! Can O Worms or what _________________ https://www.halfdonethings.com/
Tue Sep 06, 2005 3:41 pm
DumHed Experienced Roboteer
Joined: 29 Jun 2004
Posts: 1219
Location: Sydney
the score markings aren't really markings, they're the edges of each layer.
The armature is laminated like a transformer core.
I imagine it could be made out of a solid piece and work just as well (or better) but it'd be a lot more difficult and expensive to manufacture. _________________ The Engine Whisperer
- fixer of things
Tue Sep 06, 2005 3:56 pm
Valen Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
the laminations are to prevent eddy currents being formed in the stator.
if you make it out of a big peice of steel as it rotatates past the magnets it will have currents induced in it which act to counter that movement. the currents run "down" the stator (ie along the long axis) so by making it with the laminations the current cant (easily) flow down all that way and build up. instead you get much smaller eddy currents forming within each lamination.
in short you could do it but it'll hurt your efficency, i'd guess probbly 10-15% or more
only other option is a non conductive stator, your motor will go much faster but have much less torque _________________ Mechanical engineers build weapons, civil engineers build targets
Tue Sep 06, 2005 4:25 pm
Glen Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
Jake Already hit the nail on the head with the laminations they retard the eddy currents
Tue Sep 06, 2005 8:32 pm
Knightrous Site Admin
Joined: 15 Jun 2004
Posts: 8511
Location: NSW
So if I was to make a stator out of 30 layers of 0.5mm steel instead of a single 15mm thick piece of steel, it would eliminate the eddy currents.
Any info on what type of epoxy they glue/bond the laminates together with?
EDIT:
Found this stator epoxy: http://www.beaconcreates.com/TechSheets/e645tech.htm
Looks pretty funky. Was also wondering, how would an aluminium stator go. I know you would loose strength in the magnetic fields due to the lack of iron, but would it be that big of a loss? Do eddy currents form in Aluminium as well? So many questions, so little answers _________________ https://www.halfdonethings.com/
Wed Sep 07, 2005 10:50 am
Valen Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
it would *reduce* eddy currents
aluminium is not ferromagnetic, you will still have eddy currents (and i think Al is a slighlt better conductor than steel so slightly higher)
the loss of magnetic field strength would be something like an order of magnitude (ie 10x) from a hazy recoletion of the permitivity of steel and air _________________ Mechanical engineers build weapons, civil engineers build targets
Wed Sep 07, 2005 1:27 pm
Grotto
Joined: 30 Aug 2005
Posts: 38
Location: Morisset NSW
Im no expert in the inner workings of motors, but
doesnt the stator (or its vanes) 'become' an
electromaget itself when powered and thereby apply
the North/South stator field close to the permanent magnets
fixed to the casing?
By using non-ferrous stator elements dont you begin to
rely solely on the field generated by he wires? _________________ "The future is not set. There is no fate but what WE make."
........CEO Cyberdyne Systems
Thu Sep 08, 2005 12:01 am
Valen Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
yeahp
which is much weaker than the field produced by the windings + the iron.
converse to this the inductance of the non iron core will be lower so you can put more turns on (to increase the magnetic field strength) without lowering the speed of the motor. However a conductive core is still going to have a fairly high inductance (i think) so thats a loose-loose situation there. _________________ Mechanical engineers build weapons, civil engineers build targets
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